Our clinical program has recently been awarded a 4-year RO1 NIH grant HL-59490: "Aerosol Cyclosporine for Prevention of Lung Rejection". The project deals with a prospective double-blind randomized clinical trial to evaluate the effectiveness of aerosol CsA (versus placebo) combined with standard immunosuppression given for prevention of acute rejection early after lung transplantation. The clinical grant relies on biopsy histology and pulmonary function test to determine the primary end-points; no immune function tests are funded. This research proposal deals with immune correlates of rejection in this cohort of lung transplant recipients. The human lung allograft presents a unique clinical model where we can directly measure the effect of local drug delivery on the immune intragraft events associated with rejection. This proposal addresses not only "surrogate markers of disease and therapeutic effects" but will also permit us to draw important inferences regarding the "mechanism of the allograft response" to the human lung transplant. 1) We will extend our understanding of the patterns of intragraft cytokines and other effector molecules (competitive RT-PCR) and their origins (intracellular cytokine staining) following lung transplantation. Their measurements will be evaluated in stable and rejecting allografts and quantitation will be interpreted not only in lieu of systemic (oral) vs. regional (aerosol) immunosuppression but also in consideration of cytokine gene polymorphism. 2) We will study humoral allo-immunization in lung transplant recipients by following serum antibody levels against donor HLA class I and II antigens using a direct and an anti-human globulin-augmented lymphocytotoxicity assays and by an HLA-specific ELISA assay. HLA class I and II alloantibodies will be followed sequentially and related to systemic vs. regional immunosuppression. 3) We will study indirect allo-presentation by following BAL and plasma soluble donor HLA (by ELISA) in attempt to better understand its relationship to acute and chronic obliterative bronchiolitis in lung transplant recipients. The impact of aerosol CsA on the persistence of donor-specific macrophages (by flow-cytometry) will be also determined. This research project will be conducted in conjunction with the clinical trial. The project considers both cellular and humoral immune responses and has a high likelihood of providing clinical correlation of potential surrogate markers of alloreactivity. We will correlate the clinical end-points for acute rejection, chronic rejection and infection with the above laboratory parameters and determined how the sensitivity, specificity and predictive value of each assay would be clinical useful in management of lung transplant recipients.